Question: On the first 6 tests of his geometry class, Ishaan got an average score of 84. What does he need on the next test to have an overall average of 86?
Answer: Let his score on the next test be $x$ The sum of all of his scores is then $6 \cdot 84 + x$ The same sum must also be equal to $7 \cdot 86$ Solve: $x = 7 \cdot 86 - 6 \cdot 84 = 98$.